OBJECTIVES:
To study the behavior of procalcitonin and to verify whether it can be used
to differentiate children with septic conditions.METHODS:
Children were enrolled prospectively from among those aged 28 days to 14 years,
admitted between January 2004 and December 2005 to the pediatric intensive care
unit at Universidade Estadual Paulista UNESP with sepsis or septic shock. The
children were classified as belonging to one of two groups: the sepsis group
(SG; n = 47) and the septic shock group (SSG; n = 43). Procalcitonin was measured
at admission (T0) and again 12 hours later (T12h), and the results classed as:
< 0.5 ng/mL = sepsis unlikely; > 0.5 to < 2 = sepsis possible;
> 2 to < 10 = systemic inflammation and > 10 = septic
shock.RESULTS:
At T0 there was a greater proportion of SSG patients than SG patients in the
highest PCT class [SSG: 30 (69.7%) > SG: 14 (29.8%); p < 0.05].
The proportion of SSG patients in this highest PCT class was greater than in
all other classes (> 10 = 69.7%; > 2 to < 10 = 18.6%;
> 0.5 to < 2 = 11.6%; < 0.5 = 0.0%; p < 0.05). The behavior
of procalcitonin at T12h was similar to at T0. The pediatric risk of mortality
(PRISM) scores for the SSG patients in the highest procalcitonin class were
more elevated than for children in the SG [SSG: 35.15 (40.5-28.7) vs. SG:
18.6 (21.4-10.2); p < 0.05].CONCLUSIONS:
Procalcitonin allows sepsis to be differentiated from septic shock, can be of
aid when diagnosing septic conditions in children and may be related to severity.

Sepsis remains
one of the greatest challenges in critical care medicine. Despite improvements
in the understanding of its pathophysiology and despite new treatment options,
the mortality rate continues to be elevated.1

Several consensus
conferences have been held,2,3 but the criteria for defining sepsis
and related conditions are nevertheless still considered too sensitive and insufficiently
specific, which can result in erroneous or delayed diagnoses, particularly among
children. Furthermore, the clinical signs or most typical laboratory findings
of sepsis occur late on, when multiple organ system failure (MOSF) has already
occurred and mortality increased considerably, meaning that the effectiveness
of new treatment strategies are directly related to the speed with which diagnosis
is established.3,4

these problems
with definitions and diagnosis are indications of the need to focus on biochemical
mediators capable not only of distinguishing the inflammatory response to infection
from other types of inflammation, but also of indicating the severity and prognosis
of patients.

Procalcitonin (PCT),
is a prohormone of calcitonin, normally produced by thyroid gland C-cells in
response to hypercalcemia. Under normal conditions, very low concentrations
of PCT in serum (< 0.1 ng/mL) are observed.5 More significantly,
inflammatory processes induce extrathyroid production of PCT, the levels of
which increase after 3 to 4 hours, peaking at around 6 hours, with a plateau
of up to 24 hours, and can remain elevated for up to 48 hours.6

the part that PCT
plays as a mediator of sepsis has not yet been established. Some studies demonstrated
that PCT may be useful for early diagnosis and as an indicator of severity in
children with sepsis.7,8 However, several other studies have reported
the opposite results, questioning the value of PCT for diagnosis and prognosis
in patients with sepsis and septic shock.9,10 Furthermore, there
is evidence that serum PCT levels increase in patients with Systemic Inflammatory
Response Syndrome (SIRS) of noninfectious etiology.6

the conflicting
results about the role of PCT, together with the scarcity of studies of children
that have assessed this mediator, indicates that there is a need to better define
its utility for the early diagnosis of sepsis in this group. Our hypothesis
is that PCT is useful for both diagnosis and for assessing severity of children
with septic conditions after the neonatal period.

The study objectives
were: 1) to study the behavior of the serum PCT levels of children with clinical
diagnoses of sepsis or septic shock and 2) to verify whether PCT was also an
indicator of the severity of these patients, and of differentiating the children
with diagnoses of sepsis from those with septic shock, after the neonatal period.

Methods

Patients,
definitions and monitoring

This was a prospective
observational study carried out between January 2004 and December 2005, enrolling
children aged 28 days to 14 years, admitted to the pediatric intensive care
unit (PICU) at the Hospital das Clínicas, Botucatu Medical Faculty, UNESP
and diagnosed with sepsis or septic shock. Children were excluded if they had
chronic systemic inflammatory diseases, degenerative neurological diseases,
primary or acquired immunodeficiency diseases, were on corticoid therapy, nonsteroidal
anti-inflammatories or antibiotics for more than 24 hours, had suffered traumas
or burns or were in postoperative care. The study was approved by the Ethics
and Research Committee at the Botucatu Medical Faculty, Universidade Estadual
Paulista-UNESP. Written consent was obtained from parents or guardians before
recruiting their children.

Sepsis and septic
shock were defined according the criteria established by the Consensus Conference
of 2001.3 Sepsis was defined as the presence of the signs and symptoms
of SIRS associated with a documented or suspected infection. Diagnosis of SIRS
was made based on the presence of two or more of the following criteria: 1)
temperature (rectal, oral or central) > 38.5 ºC or < 35 ºC;
2) tachycardia (may be absent if there is hypothermia); 3) tachypnea; 4) white
blood cell count high or low for age (and not secondary to chemotherapy) or
immature neutrophils accounting for more than 10% of total count. In addition,
at least one of the following had to be present: altered state of consciousness,
hypoxemia, increase in serum lactate or wide pulses. Septic shock was defined
as the presence of tachycardia (may be absent if there is hypothermia) with
signs of reduced perfusion, including weak peripheral pulses compared with central
ones, altered state of consciousness or reduced urinary output. Hypotension
is a late sign and indicates uncompensated shock.

Patients were assigned
to one of two study groups on admission: sepsis group (SG) or the septic shock
group (SSG). The diagnoses of sepsis or septic shock was agreed for each patient
by a consensus of all researchers at weekly meetings. Since there is a possibility
that a patient with sepsis will progress to septic shock, the initial diagnosis
was considered the definitive criterion for assigning study group.

Patients were monitored
and given the hemodynamic support treatment recently established by a task force
set up by the College of Critical Care and Society of Critical Care Medicine.11
the vasoactive drugs employed with shock patients, and the volumes of
fluid is given during the first hour were recorded daily. MOSF was defined as
the presence of at least two dysfunctional organs diagnosed according to pre-established
criteria.12 Pediatric risk of mortality (PRISM) scores were calculated
for all patients at admission.13

Laboratory
tests

The first blood
sample was taken on admission, and labeled T0. Once 12 hours had passed, another
sample was taken and labeled T12h. The results of the biochemical analyses were
not made available to the treating doctors. The blood sample taken for PCT assay
was 5 mL at T0 and 3 mL on subsequent occasions, from central venous catheter.
After collection, the blood was immediately refrigerated and, no more than 8
hours later, the material was centrifuged so that the mediators could be assayed
in plasma.

Analysis of the
distribution of sex, foci of infection, PCT classes by time and groups and change
in PCT classes by group, was performed using the Goodman test for contrasts
between multinomial populations. Evaluation of groups by age and PRISM scores
was performed using the Mann-Whitney U test.

All conclusions
were drawn based on a 5% significance level.

Results

Inclusion
and exclusion of patients

During the period
chosen for the study, 689 patients were admitted to the PICU, 59 of whom met
the diagnostic criteria for sepsis and 65 of whom had septic shock. Twelve patients
were excluded from the SG (six were put on antibiotics for more than 24 hours,
four were postoperative patients and two had degenerative neurological diseases),
and 22 were excluded from the SSG (12 were given antibiotics for more than 24
hours, three had active chronic inflammatory diseases, two had degenerative
neurological diseases, two had been given corticoids and three died before samples
could be taken). The final sample, therefore, comprised 90 patients, 47 in the
SG and 43 in the SSG.

Comparison
of groups: general characteristics

Table
1 is a comparison of the groups by age, sex and PRISM score. The groups
did not differ statistically in terms of age or sex. They were, however, statistically
difference in terms of severity of disease, assessed by the PRISM score, which
was greater in the SSG [SSG: 29 (19.6-33.5) > SG:17.8 (16-21.7); p <
0.05].

It was possible
to isolate microorganisms in blood or cerebrospinal fluid cultures in 54 patients.
Blood cultures were positive in 40 patients, 29 (72.5%) from the SSG, and cerebrospinal
fluid cultures were positive in 14 children, 11 (78.6%) in the SSG. In 38 (70.4%)
patients, gram-negative germs were identified (P. aeruginosa; H. influenzae;
A. baumanii; and Klebsiella species), in 11 (20.4%) cases they were
gram-positive (S. aureus; S. pneumoniae; S. epidermidis)
and another four (7.4%) patients the infection was polymicrobial. A fungal infection
(C. albicans) was diagnosed in one patient (1.8%).

Table
2 shows the distribution of patients across the PCT concentration classes
at T0 and T12h for the two groups. At T0, PCT was an indicator of severity,
since it discriminated the patients with septic shock from those with sepsis,
where the majority of patients in the SSG were in the > 10 ng/mL class,
in contrast with what occurred in the SG, with the difference between groups
being statistically significant for this class [SSG: 30 (69.7%) > SG:
14 (29.8%); p < 0.05]. The proportion of SSG patients in the highest
PCT classes at T0 was significantly greater than that of patients in the other
classes [class > 10: 30 (69.7%) > class > 2 to <
10: 8 (18.6%) = class > 0.5 to < 2: 5 (11.6%) = class < 0.5:
0 (0%); p < 0.05]. In contrast, the distribution of SG patients across
PCT classes could not be differentiated statistically.

The behavior of
PCT at T12h was similar to at T0, i.e. the proportion of patients in the >
10 class was significantly greater in SSG than in SG [SSG: 35 (81.4%) >
SG: 10 (21.3%); p < 0.05]. Furthermore, there was also a statistically
significant difference between the groups for > 2 to < 10, in favor
of SG and indicating a greater number of patients from that group at lower PCT
level classes [SG = 19 (40.4%) > SSG = 4 (9.3%); p < 0.05]. Within
the SSG, a statistical difference was observed between the frequency of patients
in the highest class, compared with the other classes. In contrast, there were
no statistical differences in the distribution of SG patients across PCT classes.

Analysis of the
proportion of patients whose PCT class changed between T0 and T12h demonstrated
no statistical difference between the groups, with both groups having a predominance
of patients who remained in the same class for both samples [SG: maintained
same class = 39 (83%) > increased class = five (10.6%) = reduced class =
three (6.4%) and SSG: maintained same class = 32 (74.4%) > increase class
= nine (20.9%) > reduced class = two (4.7%); p < 0.05]. Nevertheless,
in the SSG, despite a predominance of no class change, the number of patients
who went from a lower class to a higher class was also significant.

Relationship
between PCT and PRISM score

It was observed
that the median T0 PRISM score for the 30 patients in the SSG who were in the
highest PCT class was significantly greater than the median PRISM score of the
14 SG children in the same PCT class [SSG: 35.15 (40.5-28.7) vs. SG: 18.6
(21.4-10.2); p < 0.05].

Discussion

When managing septic
patients, early diagnosis of the infection is the element which has the greatest
impact on clinical course, treatment and patient survival.14 In this
context, interest in markers of severe infection in children has been growing.

A systematic review
followed by a meta-analysis was published in 2004 investigating the value of
PCT as a marker of bacterial infection in adults and children.15
Just two of the 12 studies analyzed involved children, and one of those enrolled
newborn infants.16,17 The conclusions of the meta-analysis were that
PCT is a more accurate marker than C-reactive protein for differentiating between
viral and bacterial infections, and also for differentiation between bacterial
infection and other causes of systemic inflammation. The review left open the
question of using PCT for the diagnosis and prognosis of children with sepsis
and septic shock.

Our study demonstrated
that PCT was already capable of determining the severity of patients at the
time of admission, differentiating children with sepsis from those with septic
shock. Furthermore, we observed more elevated PRISM scores among patients with
septic shock and higher PCT levels. These results are in agreement with findings
made by Casado-Flores et al.,8 who studied 80 children with suspicion
of sepsis and observed that PCT offered better diagnostic and prognostic properties
than C-reactive protein, and that levels were significantly more elevated among
children with septic shock than among those with sepsis, and that PCT levels
were higher among patients with higher PRISM scores. Other studies have reported
similar results, identifying PCT as a marker for severity in children with meningococcal
sepsis18 and in septic newborn infants,19 in common with
studies of adults.9,20

Luzzani et al.21
studied 70 adults by means of daily PCT assays, demonstrating that this mediator
is correlated with progression to MOSF. We were unable to establish a correlation
between PCT levels and progression to MOSF. Nevertheless, we did observe that
a significantly greater proportion of SSG patients developed MOSF, when compared
with the children in the SG, and also that PCT levels were more elevated in
the SSG.

In a significant
percentage of our septic shock patients PCT levels increased as time passed,
which is behavior that may be explained by the kinetics of the mediator itself.
As was described earlier, PCT peaks later, between 6 and 24 hours, reducing
later, at from 2 to 3 days.4 It is also necessary to consider the
influence that antibiotic treatment has on PCT levels. Reductions in plasma
concentrations of this marker have been described in response to the administration
of antibiotics22 and even that PCT might be useful for testing the
response to antibiotic treatment.23 This being so, our results may
have been influenced by the use of antibiotics during the course of the disease,
and this influence may have been more accentuated in less severe cases, blocking
possible PCT increases in children in the SG.

There have been
reports that some patients without clinical symptoms of sepsis present high
PCT levels and, in contrast, that some patients who meet the clinical criteria
for the disease do not have high levels of the marker. Furthermore, that >
0.5 to 2 ng/mL PCT class (sepsis possible) has been labeled the "grey zone,"
because of the difficulties in interpreting the result. We therefore understand
that it is possible that in some of our septic patients inflammation was minimal
and that others who were initially labeled as having sepsis actually had more
severe systemic inflammatory conditions,20 explaining the observation
that some of the SG patients were in the PCT class that indicates septic shock
and some children in the SSG were in the sepsis possible class.

These data support
the statement that PCT can be considered an auxiliary method for the diagnosis
of sepsis and reflects the severity of infection. However, this diagnostic method
must be evaluated in the context of the patient's clinical status, complementing
careful clinical assessment and judgments based on other laboratory parameters,
bearing in mind that clinical diagnosis of sepsis/septic shock is very often
subjective and, consequently, uncertain. The future lies in demonstrating whether
assaying PCT improves the prognosis of patients, by making early diagnosis possible
and aiding with monitoring treatment.

Limitations
and implications of this study

There are certain
limitations to this study that merit consideration. The use of clinical diagnostic
criteria may have introduced a bias to the classification of patients. Nevertheless,
since the PCT results were kept secret, the treating physicians were not influenced
by them, meaning that the lack of a gold standard for diagnosis does not compromise
our results. Furthermore, the influence of different classes of antibiotics
on PCT levels should not be ignored, and neither should the influence of the
type of organic dysfunction and the duration of the disease. With respect to
this last factor, the clinical character of our research implies the possibility
that patients would be at differing phases of disease progression on admission,
which could also influence PCT levels. We believe that excluding children who
were on antibiotics for more than 24 hours will have minimized this effect.

The reliability
of a marker for sepsis/septic shock depends on the precision of clinical diagnosis,
which should be sought ceaselessly in order to perfect clinical definitions,
especially in children.

Conclusions

Plasma PCT levels
on admission allowed sepsis and septic shock to be differentiated, with an even
greater level of significance being possible after 12 hours, in the group studied
here. The results suggest that PCT is valid for auxiliary diagnosis of septic
conditions in children and useful as an indicator of the severity of patients.
Double-blind and randomized studies are necessary before these findings can
be generalized for the child population.

Acknowledgements

We would like to
thank the whole team at the PICU and at the UNESP Pediatrics Department's Clinical
and Experimental Research Center for helping with data collection and laboratory
analyses.

2. American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference: definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. Crit Care Med. 1992;20:86474. [ Links ]